Why do some hooks not work inside class context?

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I’m pretty stumped on this one. I’m using add_action inside my plugin class to do certain things- add scripts & styles to the head, wp_ajax, etc. Here’s the actions, in the __construct: 

function __construct(){
    add_action('admin_menu', array($this, 'sph_admin_menu'));
    add_action('sph_header', array($this, 'sph_callback'));
    add_action('sph_header_items', array($this, 'sph_default_menu'), 1);
    add_action('sph_header_items', array($this, 'sph_searchform'), 2);
    add_action('sph_header_items', array($this, 'sph_social'), 3);

    //Below here they don't work. I have to call these outside of the class (but I need class variables within the functions)
    add_action('wp_print_styles', array(&$this, 'sph_stylesheets'));
    add_action('wp_print_scripts', array(&$this, 'sph_scripts'));
    add_action( 'wp_ajax_nopriv_add_to_list', array(&$this, 'le_add_to_list'));
    add_action( 'wp_ajax_add_to_list', array(&$this, 'le_add_to_list'));
    add_action('init', array(&$this, 'register_menu'));
}

Anybody ever come across something like this? I’d really like to know how to use said hooks from within a class- it’s so messy having actions outside the class!

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2 comments

  1. Sometimes certain hooks need to be fired at certain times. Example, some hooks need to be fired upon init.

    Add this to your __construct()

    add_action('init', array(&$this, 'init'));

    Then add this function, which will contain all hooks that need to be fired upon init.

    public function init(){
    add_action('hook_name', array(&$this, 'your_method_name'));
    add_action('hook_name', array(&$this, 'your_method_name'));
    add_action('hook_name', array(&$this, 'your_method_name'));
    add_action('hook_name', array(&$this, 'your_method_name'));
}

    Another Example:

    add_action( 'init', function () {

    add_action( 'hook_name', 'function_name', 10, 3 );
    add_action( 'hook_name', __NAMESPACE__ . 'namespaced_function_name', 10 );
    add_action( 'hook_name', 'specificnamespacefunction_name', 5 );

}, 1 );

    You will want to read about the hooks and when they are fired. So you know when and where to trigger your actions. Plugin API/Action Reference

  2. This is a pretty old question, but in case anyone is looking for an answer, I had a similar issue. I had a class

    class Plugin{
  function __construct(){
    add_action('init', array(&$this, 'init'));
  }

  function init(){
    // code...
  }
}

    Plugin::init() was never getting called. I then realized my mistake. To instantiate the class I was doing this:

    if(class_exists('Plugin')){
    add_action("init", "plugin_init");
    function socialsports_init() {
      global $plugin;
      $plugin = new Plugin;
    }
}

    To fix it, I just changed the instantiation code to:

    if(class_exists('Plugin')){
    add_action("init", "plugin_init");
    function socialsports_init() {
      global $plugin;
      $plugin = new Plugin;
      $plugin->init();
    }
}

    The other option would be to use a different hook in the constructor:

    function __construct(){
  add_action('wp_loaded', array(&$this, 'init'));
}

    Or an earlier hook in the instantiation:

    add_action("plugins_loaded", "plugin_init");